Unit 02 Atomic Structure ChILL Vocabulary

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Alpha particle

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The nucleus of a helium atom, consisting of two neutrons and two protons, ejected by certain radioactive elements; positive particle. Used in the Gold Foil experiment.

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Atom

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The basic unit of matter; a neutral atom has an equal number of protons and electrons.

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Atomic mass

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The weighted average of the masses of all the naturally occurring isotopes of an element. It is the mass given on the Periodic Table.

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Atomic number

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The number of protons, determining the identity of an atom.

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Average Atomic Mass

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Weighted average of the masses of all naturally occurring isotopes. It is the mass given on the Periodic Table.

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Bohr's Model

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Electrons travel around the nucleus in well-defined paths called orbits (like planets in the solar system), shells, Principle Energy Levels (PELs) Also called the Planetary Model.

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Bright-line spectra

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Also called "emission spectrum"; lines of colored light given off by atoms as electrons fall to lower energy levels (excited- to ground-state). Like a fingerprint of an element.

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Deflected

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bounce back

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Electron

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Negatively charged particle found in orbitals around the nucleus of an atom; mass ~0, charge = -1.

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electron configuration

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The amount of electrons in each energy level. Can look up the ground state electron configuration for elements on the Periodic Table.